This invention relates to fluid railway brake control systems, and it more particularly relates to protection valve devices for such systems having spring parking brake cylinders.
Such a system is disclosed, for example, in the Spalding U.S. Pat. No. 4,033,629, granted July 5, 1977, wherein a conventional brake control system has a normally pressurized brake pipe, a control valve device with auxiliary and emergency reservoirs and a brake cylinder to control brakes of a brake rigging according to usual practice. In addition to this system, a spring parking brake cylinder is disclosed, together with a cut-out valve for preventing the contemporaneous activation of both the spring parking brake cylinder and the normal fluid pressure cylinder.
A problem arises in such a system that a parking brake may be inadvertently applied without detection by locomotive personnel, as by leakage of release fluid from a spring parking brake cylinder, causing an automatic application of the parking brakes, unnecessary wear of the brake shoes and perhaps creating a dangerous condition if this condition goes undetected in the operation of a train.
An object of the present invention is to provide a spring parking brake control system having a protection valve device which substantially obviates one or more of the limitations and disadvantages of the described prior systems.
Another object of the present invention is to provide a protection valve device for automatically indicating to a trainman that a spring parking brake may be applied in a train.
Another object of the present invention is to provide a protective valve device for sensing that a spring parking brake is applied and automatically causing an emergency brake application by venting the brake pipe.